The present invention relates to an electromagnetic clutch and pulley assembly which couples the driving movement of a flexible belt to an input shaft of an auxiliary component in a motor vehicle.
It is known in the field of automotive engines to provide an endless belt driven by an output shaft, which endless belt is used to transmit the torque of the output shaft to various vehicle components. Specifically, the belt is trained about a plurality of pulley assemblies that are associated with the input shafts of the components to be driven. Certain of such components may also be provided with a clutch assembly that is mounted on the component input shaft to be driven and used to engage and disengage the driven pulley. For example, the input shaft of an air conditioning compressor needs to be driven only when air conditioning within the vehicle is desired. When the air conditioning system is turned on, the clutch assembly engages the pulley to enable the system to be driven. When the air conditioning system is shut down, the clutch assembly disengages the associated pulley, and the pulley will no longer drive the compressor input shaft.
Typically, the clutch assemblies employed for such applications provide resilient structure, such as one or more leaf springs or one or more compression springs, that normally biases the armature plate of the clutch assembly in an axial direction away from the associated component pulley, so that the clutch armature plate remains spaced from the pulley.
When the clutch assembly is activated, a magnetic current in the coils provided as part of the pulley assembly attracts the clutch armature plate. The armature plate then moves against the force of the resilient structure and into engagement with the pulley to enable the pulley to drive the component. Typically, after the clutch plate is in engagement with and driven by the pulley, the resilient structure operates in the transmission of torque between the pulley and clutch armature.
In the instance that the resilient structure is in the form of a rubber-based or elastic material, such as a rubber-based compression spring, the resilient structure becomes subject to somewhat of a sheering action during torque transmission. This sheering action effectively reduces the useful life of the resilient structure. While metal based resilient structures may be more durable, they undesirably generate more noise during operation. In either case, because the resilient structure operates (and is subject to stress) in both the axial movement of the clutch armature plate and during torque transmission, it must be engineered to accommodate both functions. This makes it difficult to finely tune the resilient structure for its primary function, which is to resiliently bias the clutch armature plate away from the pulley, and to allow the armature plate to move into rapid, yet soft and quiet engagement with the pulley when the clutch assembly is energized.
A first object of the invention is to provide an electromagnetic clutch and pulley assembly that enables a relatively soft and quiet, yet fast engage/disengage function. The assembly provides a resilient spring member which operates in the axial direction for biasing the clutch to a disengage position, and which is independent of the torque transmitting function between the driving pulley and the driven armature mechanism. More specifically, the present invention provides an electromagnetic clutch and pulley assembly comprising a pulley member, an electromagnetic coil assembly, and a clutch assembly. The pulley member is mounted for rotation about the shaft axis, and the electromagnetic coil assembly is associated with the pulley member. The clutch assembly is constructed and arranged to selectively couple the pulley member to the shaft responsive to energizing and de-energizing the electromagnetic coil assembly. The clutch assembly includes a hub, and armature disk, torsion transmitting structure, and axially compressible resilient structure. The hub is constructed and arranged to be coupled to the shaft, and the armature disk is operatively associated with the hub. The armature disk is axially spaced from the pulley member. The armature disk is axially movable into engagement with the pulley member when the electromagnetic coil assembly is energized. The torsion transmitting structure is constructed and arranged to transmit torsional loads between the armature disk and the hub. The axially compressible resilient structure biases the armature disk axially away from the pulley member and is substantially isolated from the torsional loads.
It is a further object of the invention to provide a clutch assembly that addresses the problems associated with the prior art noted above.
In addition, it is a further object of the invention to overcome the above-noted problems of the prior art while also providing torsional damping. Accordingly, the present invention provides an electromagnetic clutch and pulley assembly for a motor vehicle engine comprising: a pulley assembly, an electromagnetic coil assembly, and a clutch assembly. The pulley assembly includes a pulley member drivable for rotation about the shaft axis by a flexible belt. The electromagnetic coil assembly is disposed adjacent to the pulley member. The clutch assembly couples the pulley member to the shaft when the electromagnetic coil assembly is energized. The clutch engagement assembly includes a hub, an armature disk, torsion transmitting structure, and axially compressible resilient structure. The hub is constructed and arranged to be coupled to the shaft, and the armature disk is operatively associated with the hub, the armature disk being axially spaced from the pulley member when the electromagnetic coil assembly is de-energized. The armature disk is axially movable into engagement with the pulley member when the electromagnetic coil assembly is energized. Torsion transmitting structure transmits torsional movement between the hub and the armature disk, the torsion transmitting structure including a rigid structure fixed to the armature disk and a resilient compression spring disposed between the rigid structure and the hub, the resilient compression spring reducing peak torsional load and dampen torsional vibration between the hub and armature disk. The axially compressible resilient structure biases the armature disk axially away from the pulley member, the axially compressible resilient structure being constructed and arranged to be axially compressible to permit the armature disk to move into engagement with the pulley member and thereby enable the armature disk to be rotatably driven by the pulley member, and hence enable the armature disk to transmit rotation of the pulley member through torsion transmitting structure to the hub and the shaft to drive the component in response to the electromagnetic coil assembly being energized. The axially compressible resilient structure is in non-torsion transmitting relation with respect to the hub and the armature disk and constituting the sole structure that biases the armature disk axially away from the pulley member, so that the sole structure which biases the armature disk axially away from the pulley member is substantially isolated from torsional transmission between the hub and the armature disk.
Another object of the invention is to provide an electromagnetic clutch assembly which is radially compact and which reduces the number of components. In accordance with the present invention, the clutch assembly has its axial and torsional coupling components all disposed within a radius defined by the innermost magnetic field dividing portion of the armature. In one embodiment, the present invention provides an electromagnetic clutch and pulley assembly for a motor vehicle engine comprising a pulley member, an electromagnetic coil assembly, and a clutch assembly. The pulley member is mounted for rotation about the shaft axis. The electromagnetic coil assembly is associated with the pulley member. The clutch assembly is constructed and arranged to selectively couple the pulley member to the shaft responsive to energizing and de-energizing the electromagnetic coil assembly. The clutch engagement assembly includes a hub constructed and arranged to be coupled to the shaft, and an armature disk operatively associated with the hub and axially spaced from the pulley member. The armature disk is axially movable into engagement with the pulley member when the electromagnetic coil assembly is energized. The armature disk has at least one magnetic field divider radially spaced from the axis, the at least one magnetic field divider being constructed and arranged to divide magnetic flux and thereby increase magnetic attraction forces generated by current through the electromagnetic coil assembly. Torsion transmitting structure is constructed and arranged to transmit torsional loads between the armature disk and the hub. The axially compressible resilient structure biases the armature disk axially away from the pulley member. The hub, the torsion transmitting structure, and the axially compressible resilient structure are disposed entirely radially inwardly of each of the at least one magnetic field divider. This construction is not only smaller, but can also be lighter than conventional clutch assemblies.
It is a further object of the present invention to provide a modular clutch assembly that can be easily adapted for several different applications. In accordance with this object, the present invention provides a clutch assembly constructed and arranged to couple a pulley member to a shaft when a electromagnetic coil assembly is energized. The clutch assembly includes a hub, an armature disk, torsion transmitting structure, and axially compressible resilient structure. The hub has a sleeve portion and a flange portion, the flange portion being fixed to the sleeve portion, the sleeve portion constructed and arranged to be drivingly coupled to the shaft. The armature disk is operatively associated with the hub, the armature disk being axially spaced from the pulley member when the electromagnetic coil assembly is de-energized, and being axially movable into engagement with the pulley member when the electromagnetic coil assembly is energized. The torsion transmitting structure transmits torsional movement of the armature disk to the flange portion of the hub, and hence the sleeve portion of the hub. The axially compressible resilient structure biases the armature disk axially away from the pulley member, the axially compressible resilient structure being constructed and arranged to be axially compressed to permit the armature disk to move into engagement with the pulley member and thereby enable the armature disk to be rotatably driven by the pulley member, and hence enable the armature disk to transmit rotation of the pulley member through the torsion transmitting structure to the hub and the shaft to drive the component in response to the electromagnetic coil assembly being energized. The hub is in contact with, but devoid of any connection to, the torsion transmitting structure and the axially compressible resilient structure.
Another object of the invention is to provide an electromagnetic clutch and pulley assembly which provides friction damping against resonant frequency vibration.
Another object of the invention is to provide an electromagnetic clutch assembly which is axially compact.
Other object and advantages of the present invention will become more apparent from the following detailed description and appended claims, wherein preferred embodiments are described.